The present invention relates to a lattice mast crane with a lattice mast boom to be luffed up in a vertical luffing plane, which comprises a pivot piece, a plurality of lattice pieces releasably connectable with each other, and a head piece.
In such lattice mast cranes, the dismantled lattice mast boom can be transported to the hoisting site and be assembled there by connecting pivot piece, lattice pieces and head piece. Advantageously, the lattice pieces, the pivot piece and/or the head piece can be bolted to each other. In the working condition of the lattice mast crane, the lattice mast boom is pivotally mounted on the uppercarriage of the lattice mast crane about a horizontal luffing axis and hence can be luffed up in the vertically extending luffing plane.
In particular, the present invention relates to a lattice mast crane with an undercarriage and an uppercarriage rotatably arranged on the undercarriage about a vertical axis, on which uppercarriage the lattice mast boom is pivotally mounted so as to be luffed up about a horizontal axis. The lattice mast crane advantageously is movable, in particular via tracked traveling gears. Furthermore, there can also be provided a derrick boom, via which the lattice mast boom is braced.
During luffing, the lattice mast boom of the lattice mast cranes described above usually is held by bracing cables. When lifting great loads with lattice mast booms (in contrast to unbraced telescopic booms), the criterion for the peak lifting capacities in a steep position is not the deflection of the boom in the luffing plane, but the lateral deformation vertical to the luffing plane, as can be illustrated with reference to FIGS. 1a and 1b. Here, the front view of two lattice booms of different width is shown schematically. FIG. 1a shows a lattice mast boom 30 which can be luffed up about the luffing axis 6 in a plane vertical to the image plane. FIG. 1b shows a lattice mast boom 31, which likewise can be luffed up about the luffing axis 6 in a plane vertical to the image plane. If the lattice mast boom 30 of the width B, which is shown in FIG. 1a, undergoes a lateral deflection S1 due to a laterally acting force Fs, e.g. a wind force, without bearing a load yet, lifting a load with the already existing deflection S1 causes a great lateral moment. If, as shown in FIG. 1b, a lattice mast boom 31 is used with a width B′, which is greater than B, the case improves, since the lattice mast boom is deformed less by the laterally acting force Fs, and hence only undergoes a lateral deflection S2<S1. Correspondingly, the lateral moment also is smaller. In addition, the stiffness of the lattice mast boom against the lateral moment generated by the load is increased due to the increased width.
In known lattice mast booms, the lattice mast is composed of the pivot piece, a single strand of interconnected lattice pieces and the head piece, so that the width of the boom corresponds to the width of the lattice pieces. To increase the lateral stiffness of such a construction, greater lattice pieces must therefore be used. To be able to lift greater loads, a completely new boom must therefore be bought, so that high investment costs are incurred for the crane operators.
In DE 10 2006 015 307 A1 it therefore is proposed to pivotally mount two booms of smaller cranes one beside the other in parallel on one large crane and connect the two booms with each other via cross-beams. For this purpose, however, the basic machine for the large crane, on which the two booms are pivotally mounted in parallel via their respective pivot pieces and which must have two winches, via which the hoisting cables of the two booms are operated, must be redesigned completely. Hence, this furthermore involves extremely high investment costs for the crane operator, since he still can use the boom, but must buy a completely new basic machine.